Their mother, Ciarra Johnson, told investigators she had made arrangements for a nearby family member to watch her children, Thompson said.

"Our investigation determined that she made no such arrangements," Thompson told USA TODAY. "That's what is so disturbing to us. There were family members around she could have called, but she just didn't bother."

Thompson said that the fire was called in shortly after 3 p.m. Monday. Johnson, 21, told authorities she had left for a 1:30 p.m. appointment. Investigators determined she actually had left the children alone since 10 a.m. that day.

Johnson, who was found locked in her car at the scene, said two gas space heaters were operating in the home when she left, Thompson said. When she returned, the single-family, wood-framed structure was engulfed in flames. Investigators also determined that the cause of the fire was the close proximity of flammable materials to a space heater, Thompson said.

Thompson said arrangements would be made for Johnson to be taken into custody in a few days.

"Needless to say, this is a tragic event that has affected the entire community," he said.